The primary super-Earth astronomers ever discovered has given off strange signals for nearly twenty years, and scientists can have finally discovered why.
Volcanoes on this hellish world periodically open up and spew hot gas that forms an environment, just for that atmosphere to burn off and leave the planet bald again, a brand new study suggests. Testing that theory will involve training the James Webb Space Telescope (JWST) on the strange exoplanet.
The planet, 55 Cancri e, is a rocky world about eight times as massive as our planet and was discovered in 2004 around 40 light-years from Earth.
The planet is so near its parent star, at lower than 2% of the space between Earth and the sun, that it makes an entire orbit in only 17 hours. This sets up some quite extreme conditions on the planet which have defied explanation.
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Perhaps probably the most puzzling aspect of the planet, as identified in a paper accepted in September to the Astrophysical Journal Letters, is the character of its transit signal. That is the sunshine visible from Earth when 55 Cancri e crosses across the face of its parent star, making a tiny eclipse, and the sunshine visible when the planet passes behind its star.
Sometimes, when 55 Cancri e passes behind its star, no visible light comes from the planet itself, while other times the planet emits a powerful visible light signal. In infrared light, there’s all the time a signal, though that signal varies in strength.
Observations of that infrared light with the Spitzer Space Telescope indicated that the day side of the planet experienced exceptionally scorching temperatures of well over 4,400 degrees Fahrenheit (2,427 degrees Celsius), while the night side had cooler, but still hellish, temperatures of around 2,060 F (1127 C).
In the brand new study, the authors hypothesize that the planet’s proximity to its star is causing it to outgas, meaning that big volcanoes and thermal vents open up, spewing hot carbon-rich elements into the atmosphere. However the planet cannot hold on to that atmosphere for long because of the acute heat, and this gas eventually gets blown away, leaving the planet bare until the outgassing begins again.
Unlike most planets, the atmosphere of 55 Cancri e is unstable. The outgassing process tries to bulk up the atmosphere, while the acute radiation and solar wind from the star blow it away. But these two processes usually are not in balance, resulting in the situation where sometimes the planet has an environment, and other times it doesn’t.
The researchers consider this imbalance within the planetary atmosphere can explain the strange transit signals. When the planet is in its atmosphere-less “bald” phase, no visible light comes from the planet’s atmosphere, because there is not one, however the planet’s hot surface still emits infrared light. When the atmosphere puffs up, each the visible light and all of the radiation coming from the surface show up within the transit signal.
While that is only a hypothesis, JWST offers a method to test it. By measuring the pressure and temperature of the planet’s atmosphere, scientists could determine whether an environment is all the time present.